Acoustical Effects of Liners in Terminal Units

We take lots of questions from designers and acoustical consultants regarding how terminal unit liners affect room sound levels. As you are probably aware, our published sound levels are based on ½” thick dual density fiberglass or EcoShield unless otherwise stated. Our TEAMS selection software adjusts the acoustical performance based on the lining material, but still many people question these results. So let’s look at the various liners.

Standard Liners – Most people consider these to be ½” dual density fiberglass or EcoShield. These materials perform almost identically with respect to both thermal insulation and acoustical performance. We therefore do not distinguish between the two when estimating sound levels.

Heavier Liners – When additional protection against condensation is desired, most people opt to go with 1” dual density fiberglass or EcoShield. For applications involving attenuators and/or fan-powered units, the additional thickness may provide reduce radiated and discharge sound levels.

Foil Liners – For critical environment applications, most people choose either SteriLoc or foil-faced EcoShield. These liners are intended to prevent insulation fibers from reaching the air stream. For this reason, these liners are installed using galvanized Z-brackets and foil tape to seal all cut edges. The foil covering reduces the sound absorption while slightly increasing the transmission loss of the casing. This could result in slightly higher discharge sound levels and slightly lower radiated sound levels.

Dual Wall – For specifications calling for dual wall construction, we offer UltraLoc. UltraLoc is solid 22g. galvanized steel over 1” dual density fiberglass. This liner is considered a heavy-duty alternative to the foil-faced liners. It is intended to prevent insulation fibers from reaching the air stream, but it is less susceptible to damage in the field. The solid inner wall prevents any sound absorption and greatly increases the transmission loss of the casing. This generally results in higher discharge sound levels and lower radiated sound levels.

Engineered Polymer Foam Insulation – For specifications calling for non-fiberglass liners, we offer FibreFree. This is a polymer foam insulation. It provides a reasonable amount of sound absorption while its density provides a slight increase in transmission loss to the casing. For most customers, the sound difference between this liner and exposed fiberglass or EcoShield would be negligible. It should be noted that EcoShield is a lower cost option when meeting non-fiberglass spec requirements.

There are many reasons why people question sound performance with regard to liners. For instance, switching the liner from ½” EcoShield to 1” EcoShield doesn’t change the sound levels of a DESV without an integral attenuator. This is surprising, but it doesn’t have any effect because the damper is at the discharge end of the casing. This means that the air stream never really comes in contact with the liner, so there’s no effect on discharge sound levels. And the extra thickness doesn’t increase the transmission loss of the casing enough to reduce the radiated sound level by any measurable amount.

If we look at that same DESV with an integral attenuator, going from ½” EcoShield to 1” EcoShield still doesn’t change the radiated sound level, but the additional casing length allows the choice of liner to reduce discharge sound levels. Sometimes people question why a particular liner doesn’t seem to provide the expected drop in sound level. That often occurs only looking at sound levels in terms of noise criteria (NC) levels. Very often sound reductions may be occurring in so-called non-critical octave band frequencies that do not change the overall room sound level. This can be deceptive because although the NC may remain the same, the overall resulting room sound quality may be improved by removing annoying high frequency tones or sound in the speech interference bands (500, 1000, 2000 Hz).

You might wonder about the effects of heavier critical environment liners like foil-faced EcoShield, SteriLoc, and UltraLoc. These liners are thicker and have a hard facing, so they tend to block or reflect sound. They don’t absorb sound energy, so they often increase discharge sound levels and render optional attenuators ineffective. They do however add enough transmission loss to the casing to lower radiated sound levels. The same is true to lesser extent for our FibreFree material. It provides sound absorption to a lesser extent than a soft liner, but the density provides some reduction in radiated sound levels.

Dual duct terminals are available with integral mixer/attenuators. The main purpose of this feature is to mix hot and cold airstreams together. Any resulting sound attenuation really only serves to reduce the amount of noise generated by the mixing process, so bear this in mind. These are really air mixers and not attenuators.

Fan-powered terminals, both series and parallel-flow, are affected differently by liner selections. Soft liners like fiberglass and EcoShield allow sound to radiate in all directions with a little additional sound coming from the induction port. Increasing the thickness of a soft liner will tend to provide a slight decrease (1-2 NC points) in radiated sound.

Estimating the effects of a high transmission loss liner like UltraLoc in a fan-powered terminal is very difficult for several reasons. First of all, this type of liner tends to block sound radiating from the top and side panels. That can reduce the chance of having low frequency noise coming out the bottom of the unit, but it tends to create a very directional and concentrated noise from the induction port. If this directional noise travels across the ceiling and is absorbed by the ceiling plenum, room sound levels could be very low. If this sound reflects off nearby ductwork or is contained by a constricted plenum space, the room sound levels could be higher.

Lab testing in accordance with ASHRAE Standard 130 is of little use when predicting the effect of these liners, because these products are tested in reverberant chambers. This type of sound room removes all directionality from the sound source, so it isn’t very useful when dealing with a directional sound source. Therefore the best way to determine the performance of a fan-powered terminal with a high transmission loss casing is through mock-up room testing. Titus offers this service to our customers whenever it is required.

Hopefully this information will help improve your understanding of terminal unit liner options and how they may impact the acoustical performance when making product selections.

For information on this topic, please contact Randy Zimmerman at rzimmerman@titus-hvac.com or Titus Communications at communications@titus-hvac.com.

Balancing Valves in a Fan Coil Application

Linear Diffuser Plenums

Displacement Calculations - Part 1

SSR Electric Heat vs Staged Heat

ECM Retrofit - Things to Consider

As most people in our industry are well aware – a newer fan motor technology can provide huge energy savings and extended service life. There are many existing buildings full of older permanent split capacitor (PSC) motors that typically last for 10-12 years in a series fan-powered unit. These motors are 20-60% efficient and service life may suffer if operating at lower speeds. As soon as these motors start showing an increasing pattern of failures, building owners who are aware of electronically-commuted motors (ECMs) may express an interest in upgrading to this newer technology. ECMs have a minimum efficiency of 80% and a service life of 25-30 years. It is possible to attempt this type of retrofit, but there are a few things to be aware of.

Were the unit models in question ever available with ECM?

If a particular unit model has been available with an ECM option, all the parts and pieces should be readily available. Of course the most important part is the motor itself and it must be programmed for a given blower cabinet. Although it may be possible to assemble parts and pieces that will fit into an existing unit, motor programming could be an issue if the unit was never developed for an ECM option. Depending on the number of units involved, it may be cost prohibitive to develop custom ECM programming for each cabinet size. One possible solution would be to factory program the ECMs for constant torque rather than pressure independent control. This could limit or eliminate the need for any development work.

Will the existing electrical service handle the ECM?

The ECM replacement will likely be rated for a different horsepower and full load current. Although the resulting operating current draw should be less than the PSC motor it replaced, motor nameplate ratings may require upsizing the supply circuit in order to provide the necessary electrical safety. Obviously, this could greatly complicate the retrofit process and add a lot of cost.

Did you know that the UL/ETL listing will be voided?

Any field modifications to a UL/ETL-listed product that results in a change of electrical characteristics such as current draw or motor horsepower will void the listing. This is true even if factory parts are field installed by factory personnel. Once a UL/ETL-labeled product leaves the factory, any changes that do not match the data found on the unit label will void the listing. The only way to reinstate the label would involve having a UL/ETL inspector visit the jobsite and field label the units. This could be very costly but may be unnecessary if local inspectors will not be involved in the retrofit process.

Have you considered the total amount of parts that will be required?

ECM retrofit doesn’t just mean replacing the motor. It generally means replacing the motor, the speed control, and blower assembly. It will likely also require additional components like power cables, communication cables, and a power filter. It could even require changing internal options like line and/or motor fuses.

Have you considered the cost of field labor required?

All of these modifications will have a field labor cost. It could easily take an hour to access each unit and swap out the various parts. It may take longer depending on the accessibility of a given unit. In an occupied building this work may need to be carried out at night or on weekends. Additional hours of electrician time would be required for any modifications to the supply circuit.

In summary

Although the temptation to upgrade from PSC motors to ECM is strong, remember that the process is not as simple as just changing motors. It involves many more parts and could require electrical work too. That doesn’t necessarily rule out the possibility on an ECM retrofit. Many building owners have contacted their local Titus representative to investigate the possibilities. ECM technology is quickly taking over this industry and it’s important to understand exactly what a retrofit may entail so that you can provide the right answers to your customers.

For information on this topic, please contact Randy Zimmerman at rzimmerman@titus-hvac.com or Titus Communications at communications@titus-hvac.com.

Thermal Displacement Diffusers

Options for Surface Mounting Ceiling Diffusers

One of the more frequently asked questions we receive in application engineering is in regards to surface mounting Titus diffusers. When a ceiling grid is not present, surface mounting is specified and the installation questions arise. Linear diffusers are available with concealed mounting, square and rectangular diffusers with square or round inlets are not.

The most important thing to know about surface mounting is that it normally requires additional framing to which the units will be secured. We often receive calls for mounting instructions after the sheet rock has been installed which is too late to provide framing without removing the installed surface. 

Framing requirements will vary from one job to the next, but there are some general guidelines and terminology we use.

Obviously installing screws in the face of a diffuser will work as it does for grilles but the duct return flanges behind diffuser edges are generally not available to provide a secure mounting base for screws. Also, many surface mount frames do not have a flat surface nor is there a screw hole fastening option available. Furthermore, screw fastening certainly does not enhance the aesthetics of the installed diffuser. 

The TRM mounting frame makes installation of grilles, diffusers and other ceiling components in plaster and sheetrock ceilings as simple as inserting them in a standard T-bar type ceiling

All sheetrock is mounted to ceiling joists. Joists are usually parallel to each other and spaced at two to three feet apart depending on local building codes, and in most cases, the framing for the diffuser can be mounted to the top of, and perpendicular to the joists. Screws are then used to mount the back pan to the framing. Framing members should be centered on the diffuser location to allow sufficient clearance for the diffuser inlet and associated duct. Additional care must be taken so as to avoid any protrusions or features that will occupy the space necessary for the framing on the rear side of the diffuser. Framing should also be at a depth that will allow the diffuser to firmly seat against the sheet rock. Most diffuser back pan heights are less than the depth of the joist. The sheet rock or ceiling surface is installed into an opening provided for the diffuser.

The diffuser core should be removed prior to installation to allow for screws to be installed in the top of the back pan transition; this is the flat portion on the rear of the back pan. Screws are then used to secure the back pan to the framing. It is helpful to use washers to prevent the screw heads from being driven through the back pan if the framing is not flush to the rear of the pan. In most cases the screws can be placed in a manner to not be visible from the occupied space after the diffuser core or face is re-installed.

The illustration above shows how the TMS diffuser would be mounted in sheetrock  

As an alternative to the framing process, and one that we suggest if the ceiling surface has been installed without prior framing for the diffuser mounting, is to use our rapid mount frame. The TRM frame can be installed in the space between the joists following the installation of the ceiling. 

The TRM replicates a standard ceiling grid module and a lay-in (type 3) frame diffuser. The diffuser can then be laid in the TRM frame. The TRM frame does add a border to the finished appearance of the diffuser, but also can be utilized as an access port to the space above the ceiling by simply pushing the diffuser up and out of the opening. 

While the TRM does represent additional diffuser cost, the reduced labor requirement and flexibility of the installation sequence offers a distinct advantage.

The TRM is available in steel and aluminum and is ordered as a separate line item. Remember, when using the TRM frame, the (type 3) diffuser frame must be used instead of the (type 1) diffuser frame.

For information on this topic, please contact Mark Costello at mcostello@titus-hvac.com or Titus Communications at communications@titus-hvac.com.

ASHRAE STANDARDS UPDATE

Titus has long been involved in ASHRAE, making contributions in the form of basic research and development as far back as the 1950’s. We still have a strong commitment to this organization and its activities. There are many Titus employees who serve on various ASHRAE committees in order to stay current on industry standards and trends as well as to have input on emerging technology. The purpose of this article is to keep you up to date with changes to several important ASHRAE standards.

Since its founding in 1894, ASHRAE has produced and maintained countless standards and guidelines related to the HVAC industry. In 2012, ASHRAE rebranded itself to expand its scope to become an international organization and to cover all aspects of the so-called ‘built environment’. Officially, these standards are updated every four years, but interim addendums are published and added as approved. Standards that cover emerging technology or critical topics such as the following are updated on a continual basis.

ASHRAE Standard 170-2017 ‘Ventilation of Health Care Facilities’

Standard 170 includes guidelines and minimum requirements to designers of health care facilities such as hospitals and clinics. The 2017 edition includes a number of important improvements to the 2013 standard:

• Adiabatic humidifiers will now be acceptable 
• Lowered requirements for exam rooms for less critical uses
• Clarification concerning the prohibition of controls to change pressure relationships between any spaces – not only airborne infection isolation and protective environment rooms
• Reduced requirements for electroconvulsive therapy procedure rooms
• Reduction in requirements for laboratories under certain circumstances
• Increased requirements for high hazard exhaust systems
• New space temperature requirements in sterile processing departments to match other industry groups
• New and clearer definition for primary diffuser arrays in operating rooms

In addition, the new edition has also been reformatted into three sections to cover hospital spaces, outpatient spaces, and nursing home spaces in order to better align the standard with Facility Guideline Institute publications that are similarly formatted.

ASHRAE Standard 55-2017 ‘Thermal Environmental Conditions for Human Occupancy’

Standard 55 sets the minimum conditions for acceptable indoor thermal environments including temperature, thermal radiation, humidity, air speed in the design, operation, and commissioning of occupied spaces. The 2017 edition includes several changes to the 2013 standard:

• Provides three compliance methods for comfort – graphical, analytical, and elevated air speed methods
• Provides a separate method for determining acceptable thermal conditions in occupant-controlled naturally-conditioned spaces
• Now uses clear and enforceable language with more easily understood requirements
• Provides clarification regarding approaches to elevated air speed calculations
• Reduces Appendix A to a single method for operative temperature calculations
• Adds a new requirement for calculating changes to thermal comfort due to solar radiation
• Includes documentation requirements and a sample form for compliance
• Standard 55 has therefore been substantially improved with the intent of clarifying its requirements and providing a clearer path to compliance.

Anyone interested in learning more is encouraged to obtain the latest editions of each of these standards.

For information on this topic, please contact Randy Zimmerman at rzimmerman@titus-hvac.com or Titus Communications at communications@titus-hvac.com.

The Case for Lynergy - SCR Heaters vs. Lynergy

An SCR controlled heater is a time proportioned heater that modulates to supply the exact amount of heat required to satisfy the zone requirements. Titus offers (2) types of SCR style electric reheat options and this article will help clarify the differences between the two. Our two SCR heater codes are the CXX and LXX codes. The CXX code is an SCR heating code that offers lower kW’s available per voltage than the LXX as well as other voltage requirements like 580V & 600V. The LXX code (Lynergy) is the Titus branded SCR heater which has more capabilities than the CXX code but no special voltages available.

CXX: 

• Utilizes an air flow sensor instead of a standard mechanical air flow switch
• 0-10v DC or AC/DC pulse
• Special voltages and lower kw options are available
• No quick ship options available

LXX (Lynergy):

• More cost effective
• Faster lead time
• Utilizes a mechanical air flow switch instead of an air flow sensor
• 0-10VDC
• 2-10VDC
• 3 point floating
• Incremental
• On/off
• 2 stage
• 3 stage
• Binary

If you are looking for very low kW or voltages higher than 480V then the CXX code will work best. For faster lead times, competitive pricing, and more control functionality then the LXX Lynergy code will be the best choice. 

• To learn more about the SCR heater platforms and Lynergy functionality you can go to the following: 
• Titus website at www.titus-hvac.com 
• Titus SCR Heat Application Guide:
•  https://www.titus-hvac.com/file/5753/AG-Lynergy-02.pdf
• Listen to the Titus Timeout Podcast for Lynergy:
• https://www.titus-hvac.com/flv/Podcast_Lynergy%20Inputs.mp4

For information on this topic, please contact Phil Baxter at pbaxter@titus-hvac.com or Titus Communications at communications@titus-hvac.com.